The water flow pattern around triangular prism artificial reefs in different distances was investigated based on CFD numerical simulation. This article mainly studied 4kinds of distances such that are 1.5,3, 4.5,6meters, which equals to 0.5,1, 1.5,2times reef length respectively. The water flow traverses two triangular prism artificial reefs in different distances at the speed of 0.2,0.4,0.6and 0.8m/s , and the flow conditions were separately studied. The results show that the wider the distance is, the larger the vortex between reefs, and the second vortex is possible to be produced when the distance is wide to a certain extent. The distance do not the second reef''s wake vortex, the two vortex structures are almost unchanged with the incoming velocity. The velocity distribution is that the velocity becomes smaller from center to periphery, but not exceed to reef height, the distribution remains unchanged in different incoming velocities.